The present invention relates to the field of perfumery and concerns more particularly a composition of matter as above-described.
It has been described in the prior art that 5-methyl-tricyclo[6.2.1.0.sup.2,7 ]undecan-4-one can be used in perfumery to develop the floral character of the compositions into which it is incorporated, as well as to provide a fixative and reinforcing effect (see, for example, U.S. Pat. No. 3,968,070).
This patent also describes a process for the preparation of 5-methyl-tricyclo[6.2.1.0.sup.2,7 ]undecan-4-one, according to the following reaction scheme: ##STR1## but has strictly no indication regarding the isomeric composition of the product thus obtained. While reproducing the described process, we discovered that the product obtained is in fact a mixture which essentially contains (1RS,5SR)-5-methyl-exo-tricyclo[6.2.1.0.sup.2,7 ]undecan-4-one, together with a minor amount, of the order of 20 to 25% by weight, of the corresponding (1RS,5RS) isomer.
Since U.S. Pat. No. 3,968,070 is perfectly silent as regards the isomeric nature of the product obtained, one has to conclude that the authors of the invention there-described totally overlooked the distinctive character of the odor of each individual isomer present in the mixture.
Yet, we have now discovered that (1RS,5RS)-5-methyl-exo-tricyclo[6.2.1.0.sup.2,7 ]undecan-4-one, having the formula ##STR2## possesses odor properties which are quite distinct from those of its configuration isomer of formula ##STR3## and, furthermore, entirely different from those of the product described in U.S. Pat. No. 3,968,070.
This discovery has been made possible as a result of the process previously cited and described in detail hereinafter, which is also the object of the invention and which makes it possible to obtain compositions of matter enriched in compound (Ia), the properties of which turn out to be clearly superior, from an olfactive point of view, to those of the prior described compositions containing essentially compound (Ib).
It has actually been ascertained that compound (Ia) possesses an aromatic odor with a strong thujonic connotation, a very natural, slightly camphoraceous and herbaceous fragrance, which is reminiscent of the odor of myrtle and cedarleaf. It is moreover a very powerful and tenacious note, both on smelling-strip and on fabrics perfumed by way of this compound.
As for compound (Ib), it has been found to possess a distinctly less aromatic-thujonic odor note, far more camphoraceous, than that of compound (Ia), with a clear fruity connotation, some aspects of which are reminiscent of rhubarb jam or jelly. This is a less powerful odor than that of compound (Ia), and distinctly less elegant in the aromatic thujonic character which is particularly prized by the perfumers.
Even if the above-mentioned odor characters are best represented in the pure or essentially pure compound (Ia), the same sought-after aromatic, thujonic, myrtle and cedarleaf connotations can be found in the odor of the mixtures of the two isomers (Ia) et (Ib) which contain a preponderant amount, i.e. more than 50% by weight, of the former. These mixtures where compound (Ia) predominates are also an object of the invention and the compositions consisting of at least about 75% by weight of (1RS,5RS)-5-methyl-exo-tricyclo[6.2.1.0.sup.2,7 ]undecan-4-one and a definite amount, but not more than about 25% by weight, of (1RS,5SR)-5-methyl-exo-tricyclo[6.2.1.0.sup.2,7 ]undecan-4-one are preferred embodiments of the invention. Such compositions can be directly obtained by the process according to the invention and are therefore economically advantageous over the pure compound (Ia), which pure compound requires the further use of preparative chromatography or fractional distillation for its preparation.
When compared with the prior art product described in U.S. Pat. No. 3,968,070, which is essentially composed of (1RS,5SR)-5-methyl-exo-tricyclo[6.2.1.0.sup.2,7 ]undecan-4-one, the compositions of the invention provide far more natural and marked aromatic-thujonic effects, as a result of the fact that the camphoraceous connotation of the prior known compound has a tendency to reduce or dampen the freshness of said aromatic notes. The fragrance effect achieved with the prior art mixture is therefore entirely distinct from that imparted by compound (Ia) of the present invention and by the mixtures enriched in this compound, a surprising result in view of the prior art, which is totally silent in this respect, and a result which is clearly apparent from the application examples presented further on.
According to the invention, compound (Ia) and the mixtures rich in this compound, i.e. which contain a predominant amount thereof, can be added to the compositions and articles that one desires to perfume in a wide variety of concentrations. The latter are dependent on the odor effect sought, as well as on the nature of the other ingredients present in a given perfuming composition. By way of example, concentrations of the order of 1 to 10%, or even 20% by weight of the compound or mixture according to the invention, relative to the weight of the perfuming base or concentrate into which they are incorporated, can be tited. Concentration values below those cited will normally be used when perfuming a variety of consumer products such as soaps, bath or shower gels, shampoos or hair-conditioners, cosmetic preparations, body or air deodorants, or yet detergents or fabric softeners and household products.
In such applications, (1RS,5RS)-5-methyl-exo-tricyclo[6.2.1.0.sup.2,7 ]undecan-4-one and the compositions of matter according to the invention can be used on their own or in admixture with other perfuming ingredients, solvents or adjuvants of current use in perfumery.
The present invention also relates to a novel process for the preparation of a composition containing a preponderant amount of (1RS,5RS)-5-methyl-exo-tricyclo[6.2.1.0.sup.2,7 ]undecan-4-one, which process comprises treating a mixture of (1RS,5RS)-5-methyl-exo-tricyclo[6.2.1.0.sup.2,7 ]undecan-4-one and (1RS,5SR)-5-methyl-exo-tricyclo[6.2.1.0.sup.2,7 ]undecan-4-one, wherein the latter is present in a preponderant amount, with a strong organic or inorganic base.
As the strong base, there will be preferentially used an alkali metal alkoxide or hydroxide, for example sodium methylate or potassium hydroxide. Other convenient strong bases are the tertiary amines, namely tributylamine.
The reaction can be carried out in an inert organic solvent such as toluene or another hydrocarbon, or yet petroleum ether. Alternatively, it can be carried out without solvent.
The reaction can take place at a wide variety of temperatures, the value of which can be easily optimized as a function of the reaction conditions and so as to guaranty a reaction rate and time adapted to industrial operation.
According to a particular embodiment, the process comprises an optional step according to which the obtained composition is subsequently subjected to preparative chromatography or to fractional distillation, so as to provide essentially pure (1RS,5RS)-5-methyl-exo-tricyclo[6.2.1.0.sup.2,7 ]undecan-4-one, i.e. with a purity above 90%.
The mixture of ketones used as starting product in the process of the invention can be prepared according to reaction scheme I, as is described in U.S. Pat. No. 3,968,070.
According to said U.S. patent, the reaction of epoxidation of 4-methyl-tricyclo[6.2.1.0.sup.2,7 ]undec-4-ene can be realized following the usual methods, namely by means of an organic peracid such as for example performic, peracetic, perbenzoic, monoperbenzoic, perphthalic or trifluoroperacetic acid, in the presence of an inert organic solvent such as chloroform, methylene chloride, trichloroethylene, dichloroethane or toluene for example.
In addition, said epoxidation can be carried out in a buffered medium. To this end, one can use an alkaline salt of an organic acid such as for example formic, acetic, propanoic, butyric, oxalic, citric, tartaric or carbonic acid.
The epoxidation reaction can be carried out at a variety of temperatures, the value of which can be optimized as a function of the reaction conditions.
The organic peracids used in said epoxidation can be prepared in situ, by treating an organic add with hydrogen peroxide, in the presence of a mineral acid, following the usual techniques [see for example: H. O. House, Modern Synthetic Reactions, Benjamin, Inc., New York (1965), p. 105 and following].
The exo isomeric configuration of the starting product remains unchanged upon this epoxidation. Moreover, the product of said epoxidation is a mixture of two isomers, represented hereinafter ##STR4##
The composition of the above-mentioned isomer mixture turns out to be practically independent of the reaction conditions.
The isomerisation of the thus obtained intermediate epoxide is carried out by treating this intermediate compound with an isomerising acidic agent. As acidic agent, there can be used an organic or mineral add, or yet a so-called Lewis acid such as BF.sub.3, SnCl.sub.4, FeCl.sub.3 or AlCl.sub.3 for example. The use of BF.sub.3 in ether solution is preferred.
Alternatively, the intermediate epoxide can also be converted into the desired ketone via treatment with a heterogeneous acidic catalyst such as an acidic diatomaceous earth, alumina, silica or other.
As previously cited, the product of this epoxidation is a mixture containing a predominant amount of (1RS,5SR)-5-methyl-exo-tricyclo[6.2.1.0.sup.2,7 ]undecan-4-one together with minor amounts of its (1RS,5RS) isomer, and it is this mixture that is used as the starting product in the process of the instant invention.
The starting compound (III)--see Scheme I-- can be prepared by Diels-Alder cycloaddition between norbornene and isoprene, as is described in U.S. Pat. No. 3,968,070, example 8a. The reaction there-described provides 4-methyl-tricyclo[6.2.1.0.sup.2,7 ]undec-4-ene strictly in the exo isomeric form.
The invention will now be described in greater detail by way of the following examples, wherein the temperatures are indicated in degrees centigrade and the abbreviations have the usual meaning in the art.